[[Image:Meat bones.jpg|300px|thumb|right|Meat bones]]
Bones are the major ingredient of stocks (except water, of course). Most of the flavour and body of stocks are derived from the bones of beef, veal, chicken, fish, and, occasionally, lamb, pork, ham, and game. (Vegetable stocks, an exception, draw their flavour entirely from vegetables.) The kinds of bones used determine the kind of stock.
- Chicken stock, of course, is made from chicken bones.
- White stock is made from beef or veal bones, or a combination of the two. Chicken bones or even pork bones are sometimes added in small quantities.
- Brown stock is made from beef or veal bones that have been browned in an oven.
- Fish stock is made from fish bones and trimmings left over after filleting. Bones from lean white fish give the best stock. Oily fish are not normally used. The term fumet is often used for a flavourful fish stock, especially one made with wine.
- Lamb, game, turkey, and other stocks have specialised uses.
Some of the proteins known as connective tissue are dissolved when cooked with slow, moist heat.
- When certain connective tissues (called collagen) break down, they form gelatin. This gives body to a stock, an important feature of its quality. A well-made stock thickens or even solidifies when chilled.
- Cartilage is the best source of gelatin in bones. Younger animals have lots of cartilage in their skeletons. As they become older, this hardens into solid bone, which is harder to dissolve into stocks. Knuckle bones, on the joints of major bones, have a lot of cartilage and are valued in stock-making. Neck bones and shank bones are also used a great deal.
Cut large bones into pieces about 8cm long. This exposes more surface area and aids extraction. Also, the bones are easier to handle.
The purpose of blanching bones is to rid them of some of the impurities that cause cloudiness. The bones of young animals, especially veal and chicken, are highest in blood and other impurities that cloud and discolour stocks. Some disagree on the importance of blanching because they feel blanching causes valuable flavours to be lost. However, many feel it is needed to produce clear white stocks. Fish bones are not blanched because of their short cooking time. If you decide that you would like to blanch your bones, this is how you do it:
- Rinse the bones in cold water. This washes off blood and other impurities from the surface. It is especially important if the bones are not strictly fresh.
- Place the bones in a stockpot and cover with cold water. Impurities dissolve more readily in cold water. Hot water retards extraction.
- Bring the water to a boil. As the water heats, impurities solidify (coagulate) and rise to the surface as scum.
- Drain the bones and rinse them well. The bones are now ready for the stockpot.
Remouillage is a stock made from bones that were already used once to make stock. The literal meaning of the French term is “rewetting.” Because not all possible flavour and gelatin is extracted from bones when making a stock, making a remouillage allows you to extract a little more value from the bones. The resulting liquid will not be as clear or flavourful as the original stock, but it does have some uses. A remouillage can be used for soups, for braised dishes, and in place of water for making stocks. It can also be reduced to a glaze and used for enriching sauces, soups, and braising liquids. To make a remouillage, discard the mirepoix and herb sachet after draining a finished stock. Add a fresh mirepoix and herb sachet to the bones, cover with fresh cold water, and simmer for about 4 hours. Drain and cool as for regular stock. This process is probably only suitable in domestic kitchens if you have an AGA or similar and are likely to keep it on for long periods, otherwise the fuel costs would outweigh the benefits of extracting that bit of extra flavour.